Our local sewing shop services everything even if you didnt buy it from them. They even do inspections for 35$ where they put a machine through its paces to tell someone if any obvious signs of a problem were apparent. They do not service it, just test everything out looking for obvious stuff. Very popular service and they are really cool about it.
Our local sewing store also does free lessons even if you didnt buy it there. It is a great way to get folks into their store, and allows them a chance at service, after market addons, and new sales opportunities that would be there otherwise.
So if you arent comfortable just plopping down and trying it out with the seller, or bring a friend who is comfy with these machines or what machines should do, see if they would do a sale contingent on inspection you pay for. 99% of the women and men on this board would probably agree to that, so it is a reasonable request.